Circuit-Breakers (CB) are well known apparatus providing overload protection for devices, especially high-power devices, like engines, lines, transformers, generators or other such things. When a current flows through a CB, heat tends to be generated due to resistance of contacts, contact stems, and electrical conductors of CB. Given the resistance as a constant, for example, R, heat generated by a current I flowing there through should be approximately I2R. In practice, the resistance R will increase along with the temperature of the contacts, the contact stems, and the electrical conductors due to the heat generated therein. Therefore, heat actually generated will be much more than that of theoretical calculation. Generally, heat generated in contacts, contact stems, and electrical conductors of a CB is disadvantages, because a high temperature raised by the heat may cause insulating elements to be worn out earlier, cause protecting electronics to function incorrectly, and even cause distortion to the contacts and contact stems, and eventually cause failure to the CB.
Therefore, how to dissipate heat generated with a CB has been a hot topic in the field for long, and various apparatus and methods have been developed for this topic.
FIG. 1 shows a polar armature disclosed in published Chinese patent application CN1427431. The polar armature comprises a polar end 2 and a polar base 3 each equipped with heat dissipating plates 9. This approach of dissipating heat applies to fixed CBs, but not to movable CBs. Further, since the polar armature is immerged in SF6 gas, insulation is not an important consideration of it.
Patent publication U.S. Pat. No. 5,753,875 discloses another approach of dissipating heat generated in a CB. In this publication, as shown in FIG. 2A, heat sinks 43 are placed on the fixed and movable contact stems to improve heat dissipation of the CB. FIG. 2B shows the construction of a heat sink 43 in detail. The heat sink 43 consists of a stack of laminations each having a central opening and radially extending slots which divide each of the laminations into a plurality of fingers. When assembled, the slots of the laminations form a plurality of axially extending passages through the heat sink. Air flowing through the passages will carry away heat from the sink, which improves heat dissipation of the CB. In practice, to dissipate heat efficiently, the size of such a heat sink should be very big, but available space for heat sinks in a CB, especially in a movable CB as shown in this publication, is quite limited. Further, charge concentration tends to be formed at corners of the fingers' tops, which is harmful to insulation of the CB.
Patent publication WO2006/040243 provides a solution to dissipate heat through a cooling element of a device for coupling one conductor to another, for example, coupling a contact stem of a CB to its moving contact. The structure of the device is shown in FIG. 3. As can be seen from FIG. 3, the structure of the coupling device is complicated, and requires additional space for the cooling element, which is a disadvantage for CBs where available space is quite limited.